What Could We Lose if a NASA Climate Mission Goes Dark?

In 2006, Isabella Velicogna and John Wahr, both at the University of Colorado at Boulder, published two studies that interpreted the first few years of Grace data; their initial paper was about Antarctica’s loss of ice, while the second was about Greenland’s, which appeared to be losing at least 100 billion tons per year. Some scientists were awe-struck. “I remember reading their first paper, and I literally couldn’t believe it,” said Berrien Moore, a dean at the University of Oklahoma who has worked on NASA missions on and off for several decades. “A quantitative measure of a mass change from year to year? It was just unheard-of.” Velicogna, now a professor at the University of California at Irvine and a J.P.L. scientist, told me that the Grace measurements didn’t suddenly make field studies of individual glaciers less important — her data couldn’t tell scientists why the ice sheet was losing mass. But they allowed her to systematically account for drastic losses in places so far-flung that they were almost impossible for human beings to reach, like parts of Greenland and West Antarctica. What’s more, the measurements enabled glaciologists to look at the decline of massive mountain glaciers, like those in Central Asia, which are a critical resource for regional water supplies. As Velicogna noted, those glaciers “could mean the difference between life and death in those places.” They can also lead to profound geopolitical conflicts. Grace soon indicated that many were shrinking.

Similar changes began to be revealed in the world’s hidden aquifers. Jay Famiglietti, a hydrologist at J.P.L. who focuses on tracking changes in groundwater — water stored in underground aquifers around the world — worked as a professor at the University of Texas at Austin in the late 1990s. Back then, a typical way to study aquifers was to monitor wells in the field. When Famiglietti was invited to meetings in Austin to hear about what Watkins and Tapley were planning, he told me: “I didn’t believe it would work. They were all talking about how we’re going to be able to see groundwater. I thought, these guys are nuts.” As the data began coming in, however, Famiglietti found that Grace could measure groundwater with astounding effectiveness. He came up with a nickname for Grace — “the scale in the sky” — and began tracking California’s water supplies during what eventually became a decade of unrelenting drought.